1. Field of the Invention
The present invention relates to a light emitting diode that is widely used for a display and the like and that has, at least, an AlGaInP light emitting layer and a transparent electrode.
2. Description of the Related Art
A light emitting diode is widely used as a device of, for example, a display, an optical fiber communication apparatus and the like. In general, required is the light emitting diode with high luminance (high output), which is excellent in light emitting efficiency and response characteristics. Furthermore, cost reduction of the products equipped with a light emitting diodes has progressed in recent years and, therefore, cost reduction is required for the light emitting diode which is a part of such products.
A variation in the color of emitted light, in addition to high luminance, is required for a light emitting diode used as a display device. Thus, a device using AlGaInP as a constituent material of a light emitting layer, emits light ranging from green to red depending on the composition ratio thereof, and is widely used. Moreover, devices having a variety of structures in addition to devices made of a variety of materials have developed in order to attain devices with higher luminance.
FIG. 1 is a schematic cross-sectional view showing an example of a conventional light emitting diode. This light emitting diode is formed on a first conductive type substrate 11 having a lower layer electrode 112 on its rear surface by sequentially laminating a first conductive type buffer layer 12, a first conductive type DBR (Distributed Bragg Reflector) layer 13, a first conductive type clad layer 14, a second conductive type light emitting layer (also referred to as “active layer”) 15, a second conductive type clad layer 16, a second conductive type first contact layer (absorptive GaAs) 17 for a transparent electrode, a first conductive type current blocking layer 18, a second contact layer (Zn layer) 19, a first conductive type transparent electrode (ITO film) 110 and an electrode (also referred to as “bonding pad”) 111 for wire bonding. Thus, this light emitting diode has the second conductive type light emitting layer 15 of a double-hetero structure, thereby increasing the light emitting efficiency; is provided with the first conductive type current blocking layer 18, thereby preventing the emitted light from being absorbed by the bonding pad; and is provided with the first conductive type transparent electrode 110 on the entirety of the surface of the device, thereby making the diffusion of current to be good and preventing the light emitting efficiency from being lowered due to the current concentration (see, for example, Japanese Unexamined Patent Publication No.HEI 11(1999)-4020 and Japanese Patent Gazette 3084364).
According to the above conventional art, however, absorptive GaAs is used in the second conductive type contact layer for the transparent electrode; therefore, a problem arises wherein the light emitting output is reduced. In addition, it is necessary to heat the substrate in order to form the ITO film and the rate of the growth of the film thereof is low; therefore, a problem arises wherein it is costly and time consuming to manufacture such a light emitting diode.